New Lights on Mineralogical and Geochemical Characteristics of Cretaceous Rocks, Gabal Qabaliat Area, South West Sinai, Egypt

Abstract

The Cretaceous sedimentary succession at Gabal El-Qabaliat range in age from Aptian-Albian to Maastrichtian. Lithostratigraphically, the succession is subdivided into Malha, Raha, Abu Qada, Wata, Matulla and Sudr formations. The mineralogy of bulk samples of Malha Formation reveals one association (quartz, kaolinite, anhydrite, muscovite and calcite followed by dolomite). The Raha Formation reveals the presence of two cycles of environmental conditions. (calcite then quartz, kaolinite and gypsum; quartz, halite, hematite, muscovite, kaolinite and gypsum). Abu Qada Formation has two cycles of environmental conditions (quartz, halite, montmorillonite, kaolinite, muscovite and calcite; quartz, anhydrite, glauconite and hematite) but Wata Formation has one cycle (calcite, dolomite and quartz). Matulla Formation has four associations (calcite, dolomite, anhydrite, hematite, quartz; calcite, dolomite, quartz, goethite, hematite and gypsum; quartz, goethite, gypsum, calcite, hematite, glauconite, kaolinite; quartz, montmorillonite, halite, anhydrite, muscovite and calcite). The clay mineralogy of Raha Formation reveals one clay association (montmorillonite, saponite and kaolinite), but Abu Qada Formation reveals the presence of two cycles of environmental conditions (lower one: kaolinite, chlorite, saponite, illite and goethite; second: montmorillonite, saponite, chlorite=kaolinite, goethite). Matulla Formation has two clay associations [montmorillonite with monor illite, saponite > kaolinite (lower cycle; middle part of this formation), montmorillonite= saponite (2^nd cycle)]. Form the geochemical studies, the variation in each major oxides and trace elements either in clastic or non-clastic rocks discussed revealing the kind of clay mineral associations and other minor components present. Two groups were identified based on CaO and MgO contents; 1^st group has > 54% CaO and low MgO including Raha, Matulla and Sudr limestones while the other group including the moredolomitic facies of Abu Qada. The dolomitic facies of Abu Qada exhibit high CaO compared with the Wata and Matulla formations. Four groups were identified based on SiO₂ and CaO contents, the 1^st group has <1% SiO₂ and > 54% CaO including Sudr, Matulla and Raha limestones; the 2^nd one has 1-2.2% SiO₂ and 47-54% CaO including Abu Qada samples; the 3^rd one has ~3% SiO₂ and 35% CaO as in Wata dolomitic limestone and the 4^th one has 27% SiO₂ and 37% CaO including dolomitic limestone of Matulla Formation. Ba and Sr contents of limestone facies reflect a separation between the different types, where Ba contents of dolomitic facies are more than their contents in limestone facies of Abu Qada, Wata, and Matulla. The Sr contents have the opposite trend where Sr content of limestone are more than that of dolomitic facies (Raha and Matulla).